1. Field of the Invention
The invention relates in general to a method of control management of production lines. More particularly, this invention relates to the use of a performance index to control and manage the production line.
2. Description of the Related Art
In semiconductor manufacture, to correctly estimate tile predetermined sales and operation target of wafer output, the control and management of production line is crucial. In the conventional operation and management of the production line, ill management is often seen to cause backlog, out of stock, or a long production cycle.
To fabricate a certain circuitry on a semiconductor wafer, tedious processes including material deposition, photolithography, ion implantation and thermal annealing required. Each of the above process has to be accurately performed to effectively produce the circuitry with required functions. Each process is correlated with another in operation time and throughput to avoid the total efficiency to be degraded due to a certain bottleneck. Therefore, each of the processes is monitored and whichever error is detected, so that the total processes can be adjusted in time for accuracy and, efficiency issues.
Effectively controlling and managing the production line is important for effectively managing each process machine, so as to avoid a single machine failure to cause lack of resources in the subsequent process or long on stock in the previous process. In addition, when a machine failure occurs, effective management and control of production can precisely indicate the effect upon the production line and accurately estimate whether it is required to speed up the on-line state of the machine. The equipment department can thus adjust the maintenance labor resources to reduce impact of machine failure.
The invention provides a method of control and management of a production line. A performance index is used to remind the production management department as a reference to avoid the occurrence of a bottleneck machine. The process throughput can thus be improved and the labor resource can be well adjusted, and the effect upon the date of product delivery can be predetermined.
In one embodiment of the invention, two kinds of performance indices are used to estimate the performance of production line. That is, the index of equipment (Ieq) and the performance index of work in progress (Iwip).
The index of equipment is used to indicate a ratio of the number of the current available machines to the target number of required machines. If the index of equipment is larger than 1.0, it indicates the number of machines can meet the requirement to achieve the predetermined throughput. On the contrary, if the index of equipment is smaller than 1.0, the available machines are not enough to achieve the predetermined throughput. Whether it is necessary to accelerate the on-line speed of the machines has to be determined.
The index of work in progress indicates a ratio of the number of semi-manufactured wafers to be finished within the remaining working hours today to a number of wafers predetermined to be manufactured today. If the index of work in progress is larger than 1.0, the target of today can be achieved. On the contrary, if the index of work in progress is smaller than 1.0, the target of today cannot be achieved. The index of work in progress can be used to estimate whether the current throughput is enough to prevent status of bottleneck machines to happen. Whether the throughput of the machine should be enhanced to speed up the process can also be evaluated.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.